Wyatt Johnston accomplished a lot for the Dallas Stars before his 21st birthday. He has already appeared in 30 NHL playoff games, with four game-winning goals over those two postseasons, and matched a single-game mark accomplished only by Wayne Gretzky. “It's unreal for sure. It's a lot of fun to watch,” Dallas defenseman Miro Heiskanen said. “He amazes us every time.” Johnston turned 21 on Tuesday, when the Stars flew home from Colorado with a 3-1 series lead in their second-round Western Confe